In forma ( from version 1.0 ) there is no Class nor file implementing “LabelLmsController”
there is an Administrator component to manage labels
so i think you jumped in a bug ( a mispelling or a wrong reference )

Labels are a different way to categorize courses, you can create them from administration > elearning > settings > label, and then assign to a course
That tab used to show a list of these "labels" to filter the courses list

Honestly, I'm not sure if we'll keep this functionality in future releases, at least not as it works now...